DIYprojects.info

harry · Guest

i am having difficulty starting my ir 10hp air compressor to start when

there is compressed air in the tank. i initially tried to run the
compressor with the 15hp rpc fitch williams helped me build 5yr ago (i
havent seen him post lately has anyone heard from him) but it had
difficulty starting it even when the tank was empty. i built a second
15hp rpc which i start with the first and only comes online when the
compressors pressure switch closes. when both rpc running and the pump

charging the tank between @100-150psi Ian=24 ,Ibn=35, Icn=21,
Vab=216,Vac=205, Vbc=225. both rpc running unlaoded 20,21,(16 for the

starting rpc 13 for the second rpc), 224,239,247. there are time delay
switches to stagger starting the rpcs and the compressor . i would
appreciate any help

DoN. Nichols · Guest

According to harry <heramsey4@cox.net>:

Ignoramus20402 · Guest

On 28 Aug 2006 16:50:39 -0700, harry <heramsey4@cox.net> wrote:

Guest · Posted: Tue Aug 29, 2006 11:20 am Post subject: Re: rotary phase converter

Harry,
Here are steps I took to address the same issue;
1. Install a time delay relay.
2. Install 2 solenoid valves. One to operate (open) the unloaders and
the other to dump all air pressure between the 2 stages, assuming that
it is a 2 stage unit.
3. Operate it off 480V by using a transformer to boost voltage.
4. Wrap heat tape around the base of the cylinders to warm them in cold
weather.

Bob

Jerry Martes · Guest

"brownnsharp" <drutstoy@sbcglobal.net> wrote in message
news:1156851336.457467.39070@m73g2000cwd.googlegroups.com...

brownnsharp · Guest

If you are running off a motor used as a phase converter, your motor on
your compressor has had a big drop in horsepower from the poor quality
of your 3 phase power. Probably most of your problem results from
this. When I put an amp-probe around my three wires from my home-made
3 phase to my milling machine, I find that the generated 3rd leg has no
current in it, and the other two legs are carrying all the current that
is running the motor.The home made 3rd leg also has noticeably lower
voltage than the 220 volts input from the power company running the
rotary converter and mill. I think you get just enough 3rd phase
from a motor type converter to start things, but the motors are really
running single phase.

I.e., I am cynical that you will ever be happy with the results you are
going to get with a rotary converter and something as hard to run as an
air compressor. Air compressors are serious loads. I bet a 10
horsepower single phase motor would cost 450 bucks new, but you might
get lucky at your local scrap yards. If I were in your shoes, I would
change the pully on my motor to get the compressor to run slower, and
settle for a compressor that is effectively 5 horsepower, not 10.

brownnsharp

brownnsharp · Guest

If you are running off a motor used as a phase converter, your motor on
your compressor has had a big drop in horsepower from the poor quality
of your 3 phase power. Probably most of your problem results from
this. When I put an amp-probe around my three wires from my home-made
3 phase to my milling machine, I find that the generated 3rd leg has no
current in it, and the other two legs are carrying all the current that
is running the motor.The home made 3rd leg also has noticeably lower
voltage than the 220 volts input from the power company running the
rotary converter and mill. I think you get just enough 3rd phase
from a motor type converter to start things, but the motors are really
running single phase.

I.e., I am cynical that you will ever be happy with the results you are
going to get with a rotary converter and something as hard to run as an
air compressor. Air compressors are serious loads. I bet a 10
horsepower single phase motor would cost 450 bucks new, but you might
get lucky at your local scrap yards. If I were in your shoes, I would
change the pully on my motor to get the compressor to run slower, and
settle for a compressor that is effectively 5 horsepower, not 10.

brownnsharp

Gunner · Guest

On 29 Aug 2006 04:35:36 -0700, "brownnsharp" <drutstoy@sbcglobal.net>
wrote:

brownnsharp · Guest

Yep. Got a bunch of caps on the idler motor. It is 10 hp, and draws 15
amps from my 220 with no caps. Caps drop the current down to 3.5 amps.
With 220 in to one winding, I get a generated 209 out. At 209 volts,
the three phase motors I hook up to the idler start and run, but draw
very little current from the lower voltage leg. Makes perfect sense to
me. If each motor rotates and generates 209 when spinning, then there
is no voltage difference between the generated leg of the mill motor
and the idler motor generated leg, and therefore no current flow. Are
you guys telling me I should hook the caps up differently? Is there
some kind of resonance phenomena which might boost the output voltage
of the idler motor? I have a huge 220 v variac transformer I have
thought about using to boost the idler motors output up to 220, but the
mill runs well enough for my purposes. (I have also ran a 3 phase motor
generator arc welder from the idler) I have had power-company 3 phase
in a previous house...and the idler motor is really a poor substitute
for the real thing. The factory-made stuff is noticeably better enough
to cause me to suspect that his compressor power problem is probably
related to the converter. If he could borrow or rent a 3 phase
gasoline generator for an hour, it would answer the power questions in
10 minutes. With no facts to back myself with, I would bet his 10 horse
motor on his compressor is about 5 horsepower with the homemade three
phase. Compressors are not tolerant of torque loss in the motors that
drive them.